Dose Reduction to the Scalp with Hippocampal Sparing Is Achievable with Intensity Modulated Radiotherapy

Area of Science:

• Radiation Oncology
• Medical Physics

Background:

• Whole brain radiation treatment (WBRT) is a common palliative approach for brain metastases.
• Protecting critical structures like the hippocampus and scalp is crucial to minimize side effects.
• Intensity-modulated radiation therapy (IMRT) offers potential for improved dose distribution.

Purpose of the Study:

• To evaluate the feasibility of combined hippocampal- and scalp-sparing IMRT plans.
• To compare IMRT plans with conventional WBRT for dose reduction to the scalp and hippocampus.
• To assess PTV coverage and adherence to RTOG 0933 constraints.

Main Methods:

• Retrospective analysis of 7 patients with brain metastases treated with WBRT.
• Contouring of brain, hippocampus, and scalp.
• Re-planning using a 9-field non-coplanar IMRT technique with specific dose constraints.
• Comparison of dose-volume histograms (DVHs) between IMRT and conventional opposed lateral fields.

Main Results:

• IMRT plans achieved acceptable PTV coverage within RTOG 0933 guidelines.
• Significantly reduced max and mean scalp dose (46% and 35% reduction in dose and irradiated volume, respectively) compared to conventional fields.
• Maintained acceptable hippocampal dose variations per RTOG 0933 protocol.
• Demonstrated feasibility of combined hippocampal and scalp sparing.

Conclusions:

• A 9-field non-coplanar IMRT plan can achieve acceptable PTV coverage while sparing the scalp and hippocampus.
• This IMRT approach shows promise in reducing radiation-induced alopecia and other scalp-related toxicities.
• Further prospective studies are needed to confirm the clinical impact on radiation-induced alopecia.